Effect of H2O and CO2on Dielectric Properties of Single‐Crystal Cordierite and Comparison with Polycrystalline Cordierite
作者:
Robert D. Shannon,
Anthony N. Mariano,
George R. Rossman,
期刊:
Journal of the American Ceramic Society
(WILEY Available online 1992)
卷期:
Volume 75,
issue 9
页码: 2395-2399
ISSN:0002-7820
年代: 1992
DOI:10.1111/j.1151-2916.1992.tb05591.x
出版商: Blackwell Publishing Ltd
数据来源: WILEY
摘要:
The dielectric constants and dielectric loss values of two naturally occurring cordierite single crystals were determined at 1 MHz using a two‐terminal method and empirically determined edge corrections. The results are as follows. Cordierite 1: κ′a= 5.653, tan δ= 0.009; κ′b= 6.106, tan δ= 0.003; κ′c= 5.658, tan δ= 0.010. Cordierite 2: κ′a= 5.765, tan δ= 0.0006; κ′b= 6.334, tan δ= 0.0007; κ′c= 5.807, tan δ= 0.0007. The agreement between measured dielectric polarizabilities as determined from the Clausius–Mosotti equation and those calculated from the sum of oxide polarizabilities according to αD(mineral) =ΣαD(oxides) neglecting the channel H2O and CO2for these two cordierite samples is ∼20%. Inclusion of the effects of water and CO2assuming mobile H2O molecules with no correlation between their dipoles improves the agreement to ∼2%. Comparison of dielectric constants of manufactured cordierite ceramics shows a discrepancy between typical observed values of 4.5–5.0 and a theoretical value of 4.0 calculated from the Clausius–Mosotti equation. In certain cases, this discrepancy can be accounted for by the presence of high‐κ′ impurities, but in others
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